This invention relates, in general to a process for producing methanol from synthesis gas. More particularly, the invention concerns reacting synthesis gas in the presence of a catalyst containing palladium and calcium under suitable reaction conditions to form methanol at high carbon efficiencies and improved rates of production.
Methanol is an increasingly important feedstock for the production of carbon-based chemicals. Existing or proposed commercial processes using methanol include dehydrogenation to form formaldehyde, carbonylation to form acetic acid, homologation to form ethanol and reactions over zeolitic materials to form gasoline-grade fractions. The presently anticipated increase in commercial methanol manufacture has underscored the need for new and improved catalysts characterized by high carbon efficiencies and good productivity to methanol.
The use of catalysts to influence the product distribution resulting from the hydrogenation of carbon monoxide is well known in the art. Among the vast array of products obtainable from the reaction of carbon monoxide and hydrogen, methane is thermodynamically the most favored, longer chain hydrocarbons are next followed by high molecular weight alcohols with methanol being thermodynamically one of the least stable products which can be formed. Hence, specific catalysts for methanol synthesis are required in order to selectively produce methanol at high reaction efficiencies from synthesis gas. The prevalent commercial catalysts today for methanol manufacture from a synthesis gas are composed of oxides and mixed oxides of chromium, zinc and copper.
Palladium is also known in the art as an effective methanol catalyst. U.S. Pat. No. 4,119,656 to Poutsma et al., dated Oct. 10, 1978, discloses the formation of hydroxylated hydrocarbons such as methanol and ethylene glycol from synthesis gas in the presence of a palladium catalyst. While the process of Poutsma et al is characterized by very high selectivities to methanol, generally about 95 percent, the productivity of methanol is substantially below that achieved in commercial methanol synthesis processes. Hence, it would be desirable to significantly improve the methanol production rate of the Poutsma et al process while maintaining its high process efficiency.
Palladium catalysts supported on carriers containing calcium, among other materials, are disclosed in the Poutsma et al patent. Specifically, Table I of U.S. Pat. No. 4,119,656 describes the various palladium catalysts which were experimentally used to produce methanol and other hydroxylated hydrocarbons, all of which catalysts were supported on Davison.TM. Grade 57 silica. At column 4, line 40 of the patent, the chemical analysis of such silica is provided and shown to contain 0.03% CaO (corresponding to 0.021% Ca). Hence, the use of palladium catalysts containing 0.021% Ca for methanol manufacture from synthesis gas has been reported in the prior art.